Biogas plants are constructed using different technologies according to the planned purpose. The classification of biogas plants, as per their digester capacity, is as follows:
Family type: 6 - 12 m3
Farm type: 50 - 100 / 150 m3
Village type: 100 - 200 m3
Industrial scale plants: 1,000 - 10,000 m3
Family type biogas plants are widely used in China, especially in rural areas. In most plants, other than family type small ones, heating of the environment in which biogas is formed (digester) is required for optimum biogas production. In the production of biogas, the ambient temperature should be around 35°C. In order to provide heat control in biogas plants, the most practical and widely used system is hot water coils installed inside the digester.